on Size, Energy and Unit, we know that the speed of light better be equal to 1, that simplify the equation of relativity.
now, we impose 1 more things, the Reduced Planck constant, also set to 1. that simplify all equations with angular momentum or spin.
the Angular momentum:
now becomes :
when we want to calculate the real value, we can recover the by considering the dimension. the reduced Planck constant has dimension